There are many situations where an acceleration of the setting for a mortar or a concrete composition based on Portland cement and/or on calcium aluminate cement is expected. This is the case especially for the building or the repair of civil engineering works, such as street or road pavements, sidewalks. To be also mentioned are maintenance and construction of electric cable networks, pipe networks for gas and water distribution. Repair works for technical facilities often require underground cavities to be dug, which are sources of complications for the users of such facilities. Thus, it is essential for such cavities to be rapidly filled, so that said facilities can be put in service again as soon as possible after the end of the works.
During the recent years, the composition of cement-based systems has changed in favor of concrete formulations based on amorphous calcium aluminate enabling to obtain a (very) high initial strength thanks to their ultra-reactivity.
The document CN 102 765 738 describes for example an amorphous calcium aluminate composition, as well as the method for making the same. Amorphous calcium aluminate may be used as an additive for a cement-based composition, so as to improve its setting time or as an additive for steel production. In particular, amorphous calcium aluminate comprises, by weight, as compared to its total weight, from 40 to 60% of CaO (C), from 30 to 60% of Al2O3 (A), from 0.01 to 1% of S, from 1 to 10% of SiO2, from 0.05 to 3% of Fe2O3, from 0.01 to 5% of CaF2, from 1 to 10% of MgO, from 0 to 3% of TiO2 and from 0.01 to 1% of P.
The ultra reactivity of amorphous cements in turn is made possible thanks to a very fast dissolution rate of this cement type when they are put in contact with water. Despite everything, such a high affinity with water makes it difficult to preserve the reactivity of these ultra-reactive cements, and of the formulations containing the same, especially under damp conditions.
It is thus an objective of the present invention to provide a new ultra-fast setting cement composition especially based on amorphous calcium aluminate, combined or not with other mineral binders such as Portland cement or calcium sulfate which avoids, at least partially, the abovementioned drawbacks.
In particular, the present invention aims at providing a new ultra-fast setting cement composition with an improved shelf-life and furthermore not impairing the properties of the mortar or concrete obtained from such a cement composition.